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Name: _________________________________________________ Period: _____ Genetics…Punnett squares and More! Directions: Solve each problem below. Write out complete phenotype and genotype ratios for each cross [when asked for]. The Basic Punnett Square (Autosomal Monohybrids) 1) In the space below, cross two individuals that are heterozygous for a green pea pod. What are the genotype and phenotype ratios for this cross? Phenotype: ____________________ Genotype: ____________________ 2) 1) In fruit flies, the gene for red eyes (R) is dominant and the gene for sepia eyes (r) is recessive. What are the possible combinations of genes in the offspring of two red-eyed heterozygous flies (Rr)? 3) In certain breeds of dogs, deafness is due to a recessive allele (d) of a particular gene, and normal hearing is due to its dominant allele (D). What percentage of the offspring of a normal heterozygous (Dd) dog and a deaf dog (dd) would be expected to have normal hearing? 4) In a certain species of plant, the color purple (P) is dominant to the color white (p). According to the Punnett Square, what is the probability of an offspring being white if both parents are heterozygous? 5) In a certain species of pine trees, short needles (S) are dominant to long needles (s). According to the Punnett square, what is the probability of an offspring having long needles if one parent is homozygous dominant and one is homozygous recessive? Name: _________________________________________________ Period: _____ The Basic Punnett Square (Autosomal Dihybrids) Example: A tall green pea plant (TTGG) is crossed with a short white pea plant (ttgg). TT or Tt = tall tt = short GG or Gg = green TG TG TG tg TtGg TtGg TtGg TtGg tg TtGg TtGg TtGg TtGg tg TtGg TtGg TtGg TtGg tg TtGg TtGg TtGg TtGg gg = white TG 16 Tall/Green : 0 Tall/White : 0 Short/Green : 0 Short/ White 1) A tall green pea plant (TTGg) is crossed with a tall green pea plant (TtGg) ____ Tall/Green : ____ Tall/White : ____ Short/Green : ____ Short/ White 2) A tall green pea plant (TtGg) is crossed with a Short yellow pea plant (ttgg). ____ Tall/Green : ____ Tall/Yellow: ____ Short/Green : ____ Short/ Yellow Name: _________________________________________________ Period: _____ 3) A Heterozygous (for both traits) tall red flowered plant is crossed with a homozygous (for both traits) short white flowered plant. Tall and red are both dominant traits. ____ Tall/Red : ____Tall/White : ____ Short/Red : ____ Short/White 4) Two Heterozygous Tall, Green pea plants are crossed. Yellow and short alleles are recessive. ____ Tall/Green : ____ Tall/Yellow : ____ Short/Green : ____ Short/ Yellow Chi Square Genetics Problem 5) A student performed a genetics experiment with fruit flies. He started with red-eyed heterozygous fruit flies (white eye color is recessive). After allowing the fruit flies to mate, he documented the phenotypic traits of the offpsring. He found that 80 were red-eyed and 20 were white eyed (out of 100 total offspring). Run a Chi-square test to see if he should accept or reject his null hypothesis. Null Hypothesis: There is no difference between the expected outcome (3:1 ratio) and the observed fruit fly phenotype outcome. Outcome Observed Expected (O-E) (O-E)2 (O-E)2/E Red Eyed White Eyed Chi Square Value Total χ2 Accept or Reject Null Hypothesis: __________________________________________________________
